I used to work in the kitchen showroom of a design center that had locations throughout the country. My job was to sell the idea of doing the project to potential customers and answer all the questions to help them decide whether they wanted to hire our firm to do the project. I would do square foot takeoffs if they brought in their measurements and selected a cabinet company from our choices. We also sold appliances, countertops, tiles, lighting, sinks, cabinet hardware and flooring at our location. The whole package. We also handled local permits for you. We also offered full installation or the customer could use his own contractor and then we would just order the products.
Our statistics indicated that an average kitchen in the US ran about $45,000. That proved true in our location but since we were located in a high-end area we did have several kitchens per year that reached $100,000+. It, of course, depends on square footage of the room, the level of cabinetry selected (KraftMaid was considered our entry level company and we also offered high-end cabinets where custom crafted cabinets out of specialty woods could be ordered and they would easily double the price of our entry level cabinets), which appliances you select, etc. Granite countertops, for instance, ran from $49 per sq. ft. to over $100 per sq. ft. depending on the rarity of the stone selected and the edge choice and how many penetrations in the top for sinks, etc. Engineered stone (quartz) was similar in price.
In you need structural changes to your plan (removing a load bearing wall or column, for instance), it becomes a more complex design issue than if you were just replacing item for item. You need an architect in that case to prepare the plans. Also there are issues that arise once you begin demolition that were not apparent until walls, old cabinets, etc. were removed, depending on the age of the home. There could be water damage, for instance.
There is also the matter of local codes. Sometimes demolishing a room can mean that you now have to replace all of the electrical or plumbing to meet code which you wouldn’t have had to do if you just left it all alone.
All of this is just a simple explanation of why estimates are just that–estimates–and you may not know the final cost until the contractor gets going.
Our sales pitch was that you would re-coup your investment when you sold your property but the truth is you cannot count on the full price. The value of your home is based, in part, on the neighborhood where it is located. If all the surrounding homes are worth, for example, $200,000, installing a $100,000 won’t bring you $300,000.
Hope this helps in your planning. 